1. Field of the Invention
The present invention is directed to an image processing apparatus for manipulating an image, such as copier, printer, scanner and so on.
2. Description of the Related Art
Presently, a JPEG format has been generally used as an encoding format to compress a still image, which compresses an image data using a discrete cosine transform. However, in late years, for the purpose of providing improved compression performance and extended function, development and distribution of a JPEG 2000 format has been promoted, which compresses an image data using a wavelet transform. As a feature of this JPEG 2000 format, it is known to optionally identify a specific region in image data as a region of interest (hereinafter, referred to as ROI) by encoding the specific region prior to other regions to allow the specific region to be recognized roughly at an initial stage in transmitting the image data, or by encoding the specific region in image data in higher quality than other regions, as disclosed in Japan Patent laid-open publication 2001-218062.
However, generally, for example in case of printing a JPEG 2000 file including a ROI, it tends to become difficult to identify a ROI from a printed image if an image data has a ROI of which its boundary is obscure, if a plurality of ROIs are included in image data, or if ROI is a relatively small region.
To resolve this problem, as a method for bringing the ROI into clear view by adding an outline to ROI, it is known to generate mask information indicative of position for pixel set to ROI from quantized values of frequency transform coefficient (Wavelet transform coefficient) and perform bitmap decompression. However, this method has a defect that high-capacity storage area is needed to store a ROI mask information.